Heart disease is a leading cause of morbidity and mortality in children. A network of research centers with both a sufficient clinical population and team of researchers trained to conduct multi-center trials could provide standardized, blinded, quality research that has the statistical power to change the way children with heart disease are managed. Primary Children?s Medical Center, located in Salt Lake City, Utah, is uniquely qualified to participate as a research center within such a network. It serves as the leading referral hospital for children with heart disease in the Intermountain West. The overall goal of the proposed Intermountain Pediatric Heart Disease Research Center is to collaborate in prospective, randomized, multi-institutional trials that provide robust data leading to the advancement of knowledge regarding pediatric heart disease and evidence-based pediatric medicine. The specific aims of the Intermountain Pediatric Heart Disease Research Center are: to propose scientifically sound, statistically robust research protocols that can be performed within the Pediatric Heart Disease Clinical Research Network; to enroll eligible children at Primary Children?s Medical Center; and to collect complete data and readily communicate results within the Pediatric Heart Disease Clinical Research Network so as to facilitate the rapid dissemination of research findings. We propose two clinical studies for the Pediatric Heart Disease Clinical Research Network. The overall goal of protocol 1, "Efficacy of Abciximab in Treating Children with Large Coronary Aneurysms," is to compare the effectiveness of abciximab added to conventional therapy versus conventional treatment alone for dissolving or preventing thrombi and for facilitating remodeling in large coronary artery aneurysms attributed to Kawasaki disease, The overall goal of protocol 2, "Decellularized Human Allograft Valve Preparation (Cryovalve SGR) versus Standard Cryopreserved Valved Allografts for Vascular Reconstruction in Children," is to determine the function and long-term durability of decellularized human allograft valve preparation versus the current state-of-the- art cryopreserved valved allograft. The investigators agree to enthusiastically participate in and diligently adhere to any protocol selected by the Pediatric Heart Disease Clinical Research Network. The applicant organization, Primary Children?s Medical Center, agrees to the per patient capitation of operational costs for the study protocols selected by the Pediatric Heart Disease Clinical Research Network.